Spark plugs have been used for internal combustion engines. These spark plugs have electrodes that form a gap. The electrodes used are, for example, electrodes having noble metal tips, in order to restrain consumption of the electrodes. One technique proposed to restrain an increase in the temperature of a center electrode is to join a noble metal tip to a shaft having a copper core embedded therein. With this technique, the increase in the temperature of the noble metal tip is restrained, and the consumption of the electrode can thereby be restrained.
However, long-term use may cause consumption of the noble metal tip. When the noble metal tip is consumed, discharge may not be generated appropriately. This problem is not specific to the center electrode but is common to the center electrode and a ground electrode.
The present disclosure discloses a technique for restraining consumption of an electrode.